1. Field of the Invention
The present invention relates to a new antigenic protein capable of causing delayed hypersensitivity reactions of different intensity in the presence of living or dead bacteria of the Mycobacterium tuberculosis complex, its diagnostic and therapeutic applications especially as vaccine.
This Mycobacterium tuberculosis complex comprises four species: Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium africanum, Mycobacterium microti (le Minor et Veron; bacteriologie Madicale 1990, 2nd ed. p. 1966).
2. Discussion of the Background
The delayed-type hypersensitivity reaction to tuberculin is used commonly as means of diagnosing tuberculosis. This tuberculin challenge is particularly used as diagnostic means in the United States and in the Netherlands, countries where BCG vaccination does not or no longer exists. A recent development (1990) by the American Thoracic Society recommends in particular the use of this diagnostic test and specifies its limits for the national campaign for the total eradication of tuberculosis which is being put in place in the United States. For France, the medical practice is a little different because of the wide use of BCG and the still relatively high frequency of tuberculosis. The reaction to tuberculin is used to monitor secondary sensitization to the vaccination and also to provide arguments in favor of the existence of a tubercular infection. This diagnostic indication is based on the clear increase in the intensity of the reaction in a given subject or on the very high intensity of the reaction. But this quantitative notion is difficult to assess accurately when the tuberculin reactions are performed and/or read by different people.
In fact, the delayed-type hypersensitivity skin reaction to tuberculin does not currently allow sick subjects having a developing tuberculosis to be differentiated with certainty from previously sensitized subjects. Indeed, subjects carrying numerous living bacilli (patients suffering from tuberculosis or recently vaccinated subjects) may present the same skin reactivity to tuberculin as subjects who have been previously sensitized by a primary infection cured spontaneously or having suffered a tuberculosis which is now cured.